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A1989 - 820-00850 - Stucks at 5V -> Missing PPBUS_G3H on single port

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dudipupan

Member
Hi there,

currently I'm working on a MBP A1989. It was my testing-device for repairs and ironically it just stopped working :-D
When I got it, 2 years ago, the logicboard was slightly bent on the top left corner (corner of the Touch-ID) but it worked well for two years.
Now it stucks at 5V. Im getting 5V 550mA on 3 of 4 ports. The last one is at 5.1V 170mA and PPBUS_G3H is missing on this single port. PPBUS is present when plugging it in with the other 3 ports.
Does anybody has an idea what could cause this?

Thank you very much and a happy new year to everybody :)
 
2informaticos

2informaticos

Administrator
Staff member
Check PPBUS_G3H with just charger connected (no battery).
Test it out of the shell.
Use 87/96W original charger.

Also compare diode mode readings on the LDOs of bad port with any other.
PLEASE, don't make "cardinal refferences"; use corresponding component position in the boardview/schematic.
 
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dudipupan

Member
Thank you for your reply. The measurements were made out of the shell, without battery. I did get the same results when i initially tested it, inside the case with battery. The charger is the original one :)

I will check on the LDOs and post the results.
Ok, sorry, I won't do it again ;-)
 
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dudipupan

Member
I did the measurements and found the fallowing differences between the LDOS of the bad one (UB300), compared to the others:
PP1V8_UPC_TA_LDOD = 0.434 is lower than the others (=0.465)
PP3V3_UPC_TA_LDO = 0.218 is much lower than the others (=0.402)

Measuremnts on PP1V1_UPC_TA_LDO_BMC and PP1V8_UPC_TA_LDOA are "good".
 
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